Method for Producing Back-Tapers on Teeth of a Gearing of a Workpiece in the Form of a Gearwheel

ABSTRACT

A method for simultaneous production of at least two back-tapers on the teeth of a workpiece in the form of a gearwheel using a tool that includes a tool carrier configured in elongated manner, in the manner of a journal, and oriented coaxial to a central longitudinal axis of the tool, and at least two blades, which come into engagement with the tooth to be machined, removing chips during use, wherein the blades are held on the tool carrier at a distance from one another in the longitudinal direction of the tool carrier and a width of the blades extend over a partial length of the tool carrier. The position of at least one of the blades is adjustable in relation to the other blade, so as to balance out deformations of the tool carrier that occur during use.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.17/353,985 filed on Jun. 22, 2021, which claims priority to GermanPatent Application No. 10 2020 116 413.0 filed Jun. 22, 2020, thedisclosures of which are hereby incorporated by reference in theirentireties.

BACKGROUND OF THE INVENTION Field of the Invention

The invention relates to a tool for producing back-tapers on teeth of agearing of a workpiece in the form of a gearwheel, wherein the tool hasa tool carrier configured in elongated manner, in the manner of ajournal, and oriented coaxial to the central longitudinal axis of thetool, and comprises at least two blades, which come into engagement withthe tooth to be machined, in each instance, removing chips during use,wherein the blades are held on the tool carrier at a distance from oneanother in the longitudinal direction of the tool carrier and extendover a partial length of the tool carrier.

Description of Related Art

Likewise, the invention relates to a method for simultaneously producingat least two back-tapers on one of the teeth, in each instance, of agearing of a workpiece in the form of a gearwheel, by means of a tool ofthe type explained above.

Typically, the gearwheels to be machined using a tool according to theinvention or by using a method according to the invention are what arecalled “sliding sleeves.” These are needed in manual transmissions ofvehicles that are driven by an internal combustion engine. In order toensure that the workpiece in the form of a gearwheel, which is broughtinto engagement with the sliding sleeve for a transfer of force, remainsin engagement with the sliding sleeve even under the great forces thatoccur during use, what are called “back-tapers” are usually formed onthe tooth flanks of at least some of the teeth of the sliding sleeve.These shape elements, configured in the manner of recesses or shouldershaving a precisely determined geometry, prevent unintentional axialdisplacement of the workpiece in the form of a gearwheel that mesheswith the sliding sleeve. In this regard, the back-tapers are typicallyformed on the end regions of the tooth flanks of the teeth of thegearing that are adjacent to the corresponding end face of the workpiecein the form of a gearwheel.

A tool and a method of the type indicated initially are known from DE10127 973 A1, for example. The use of a tool that comprises two blades, aspresented there, allows producing two back-tapers on the gearwheel atthe same time. For this purpose, in the state of the art the blades arearranged in a line that is oriented axis-parallel to the centrallongitudinal axis of the tool, which line agrees with its axis ofrotation, wherein the width of the blades, measured in the longitudinaldirection of the tool carrier, corresponding to the width of theback-taper to be cut by them into the corresponding tooth flank, and thedistance between the blades corresponds to the distance that is supposedto exist between the back-tapers to be formed on the corresponding toothflank. At the same time, the blades can additionally be configured inaccordance with the shape of the back-tapers to be formed. If, forexample, back-tapers having a depth that increases proceeding from theedge of the back-taper assigned to the corresponding end face of thegearwheel, in the direction of the center of the width of the toothflank provided with the back-tapers, then this can be accomplished bymeans of blades having a thickness that increases in a correspondingmanner, proceeding from their narrow side assigned to the correspondingend face of the gearwheel, in the direction of the opposite narrow side,so that the blade has a cutting edge that runs at a slant in a top viewof the blade.

In order to guarantee problem-free functioning during use of a workpiecein the form of a gearwheel, provided with back-tapers, the shape,location, and orientation of the back-tapers must agree precisely withthe required values that result from the design of the gear mechanism.Adherence to this requirement proves to be difficult if the forces thatoccur during use are so great that the tool itself or the tool holder inwhich the tool is clamped during use are deformed. Such deformationsoccur, in particular, if the tool carrier has a great length that leadsto great bending stresses or torsion stresses as a result of thetransverse forces that occur during chip-removing machining of thecomponent in the form of a gearwheel.

Tools held in a tool carrier having an enlarged length and, as a result,an enlarged projection with reference to the clamp in which they areheld, are used, for example, for machining tooth flanks of teeth ofsliding sleeves or comparable gearwheels, which are comparably wide.Such wide gearwheels are needed, for example, in manual transmissions ofheavy machines, so as to be able to absorb the great forces that occurduring their use. In order to be able to produce two back-tapers onselected teeth at the same time on such wide gearwheels, a tool must beused having a tool carrier that possesses a length that corresponds tothe width of the workpiece in the form of a gearwheel. The slim,elongated shape of the tool carrier that results from this, inparticular, brings with it the risk that the tool carrier or the toolholder that holds the tool deforms during machining. This deformationcan consist of bending transverse to its central longitudinal axis or intwisting of the tool about its central longitudinal axis, wherein thesetypes of deformation can also be superimposed.

Against the background of the state of the art as explained above, thetask has arisen of creating a tool that allows highly precise,simultaneous production of two back-tapers on the tooth flanks of theteeth of a workpiece in the form of a gearwheel, independent of theirwidth.

Likewise, a method is supposed to be stated, which makes it possible toproduce two back-tapers on the tooth flanks of teeth of a workpiece inthe form of a gearwheel, with great precision, simultaneously, evenusing a tool that has a delicately formed, elongated tool carrier.

The invention has accomplished this task by means of the tool asdescribed herein.

Advantageous embodiments of the invention are indicated in the dependentclaims and will be explained in detail below, as will the general ideaof the invention.

SUMMARY OF THE INVENTION

A tool according to the invention, for producing back-tapers on teeth ofa gearing of a workpiece in the form of a gearwheel, accordinglycomprises, in harmony with the state of the art as presented initially,a tool carrier configured in elongated manner, in the manner of ajournal, and oriented coaxial to the central longitudinal axis of thetool, and having at least two blades, which come into engagement withthe tooth to be machined, in each instance, removing chips during use,wherein the blades are held on the tool carrier at a distance from oneanother in the longitudinal direction of the tool carrier and extendover a partial length of the tool carrier, in terms of their width.

According to the invention, in the case of such a tool the position ofat least one of the blades is now adjustable in relation to the otherblade, so as to balance out deformations of the tool carrier that occurduring use.

In a corresponding manner, in the case of a method according to theinvention, at least two back-tapers are produced simultaneously, in eachinstance, on the teeth of a gearing of a workpiece in the form of agearwheel, by means of a tool that rotates about its centrallongitudinal axis, wherein the tool comprises a tool carrier configuredin elongated manner, in the manner of a journal, and oriented coaxial tothe central longitudinal axis of the tool, and at least two blades,which come into engagement with the tooth to be machined, in eachinstance, removing chips during use, wherein the blades are held on thetool carrier at a distance from one another in the longitudinaldirection of the tool carrier and extend over a partial length of thetool carrier, in each instance.

According to the invention, a tool according to the invention is nowused for such a method, and based on this at least the following worksteps are completed:

-   -   a) determining the bending deformation and/or torsion        deformation that the tool carrier or the clamp in which the tool        is held experiences during production of the back-taper;    -   b) adjusting the position of an adjustable blade of the tool        with reference to the other blade of the tool, in each instance,        taking into consideration the deformation determined in work        step a), in such a manner that the position and the shape of the        back-tapers to be produced on the teeth of the gearwheel type        meet a required value, in each instance;    -   c) producing the back-tapers on the teeth of the workpiece that        is in the form of a gearwheel.

With the invention, a back-tapering tool is therefore available, whichallows simultaneous production of two back-tapers on the teeth of aworkpiece in the form of a gearwheel, which workpiece is typically asliding sleeve for a manual transmission. In this regard, the toolaccording to the invention allows production of back-tapers that fulfillthe strictest demands with regard to their geometry, position, andorientation, even in the case of particularly wide teeth, which requirean elongated, slim tool carrier. This particularly relates to theangular positions of the back-tapers, for which it is possible toguarantee optimal agreement with the corresponding required values,using a tool according to the invention.

The invention proceeds from the recognition that it is not necessary tostiffen the tool carrier or the tool holder for precise formation of twoback-tapers on a tooth flank of a tooth of a gearwheel, in such a mannerthat they do not deform under the forces that occur during use. Instead,it is sufficient, according to the recognitions of the invention, toorient at least one of the blades on the tool carrier of a toolaccording to the invention, with reference to the other blade, in eachinstance, in such a manner that geometry errors are corrected, whicherrors would unavoidably occur, without a suitable counter-measure, as aresult of the deformation of the tool or the tool holder, whichdeformation is accepted according to the invention.

In order to allow such orientation with the greatest possiblevariability and, accompanying this, to make a tool according to theinvention suitable for machining different types of workpieces in theform of gearwheels, in particular sliding sleeves, and for use indifferent machines having different workpiece holders, in the case of atool according to the invention, the position of at least one of theblades can be changed with respect to the other one, in each instance.

Typically, in the case of a tool according to the invention, the firstblade is fastened to a region arranged on the free end of the toolcarrier, while the second blade is arranged in the opposite end of theend region assigned to the tool carrier, which region generally followsa mounting pin that serves for clamping the tool in a tool holder. Inthis regard, a circumferential shoulder can be provided between themounting pin and the tool carrier, which shoulder forms the transitionbetween the tool carrier and the mounting pin. In this regard, thecircumferential shoulder can be formed in the manner of a collarprojecting in the radial direction relative to the pin, which collarforms a stop up to which the mounting pin can be pushed into the toolholder.

In the case of a tool according to the invention, the greatestdeformations occur in the region of the free end of the tool, due to itsslim shape. For this reason, at least the position of the blade providedthere is adjustable, in a manner according to the invention, so as tocompensate for the shape errors of the back-tapers to be produced,otherwise caused by the deformation of the tool carrier or of the toolholder. In contrast, the other blade, arranged close to the clampinglocation of the tool, can generally be mounted in fixed manner, becausein practice, only negligible deformations of the tool carrier occur inthe region closely adjacent to the clamping location. The blade that isfixed in place on the tool carrier in this embodiment and mountedunchangeably close to the mounting pin provided for clamping then formsa fixed reference point for adjustment of the blade that can bepositioned in changeable manner. In this way, adjustment of the positionof the adjustable blade becomes particularly simple. In contrast, forexample in the case that the significant part of the deformation takesplace in the tool holder, it can also be practical to make each of theblades of a tool according to the invention adjustable. In this way,even the complex shape errors of the back-tapers to be produced can bebalanced out, which would be produced by the deformation of the toolholder and the related position deviation of the tool from its requiredposition.

As a function of the deformations of the tool carrier that occur duringuse, it can be practical to provide for adjustability of the adjustableblade with reference to the central longitudinal axis of the tool, inthe radial direction (to compensate for bending of the tool carrier orof the tool holder) or adjustability of the adjustable blade in thecircumferential direction of the tool carrier (to compensate fortwisting of the tool carrier), wherein these two possibilities ofadjustment of the position of the blade that is adjustable, in eachinstance, can also be combined with one another.

The deformation of the tool or of the tool holder that occurs as theresult of bending deformation and/or torsion deformation, and theaccompanying deviation of the position of the blades, in particular ofthe adjustable blade, from the required position, which deviation occursduring use, based on the stresses that occur then, can be determined inwork step a) of the method according to the invention, by means ofpractical tests or by calculation, for example by means ofcomputer-assisted simulation, in known manner.

Setting the position of the at least one adjustable blade of the tool,in each instance, with reference to the other blade of the tool, in eachinstance, then takes place in work step b), taking into considerationthe deformation determined in work step a), in such a manner that theposition and the shape of the back-taper to be produced on the teeth ofthe gearwheel type fulfill a required value, in each instance.

For the adjustment, the adjustable blade, in each instance, can be heldon a carrier that can be positioned in different positions on the toolcarrier, for example by means of a releasable connection that acts withforce fit and/or shape fit, such as, for example, a screw connection ora clamped connection.

In the case of a correspondingly adjusted tool according to theinvention, the position of at least one of the blades deviates from therequired position in the unused, unstressed state. However, thisrequired position occurs automatically during machining of the workpiecein the form of a gearwheel (work step c)) during use, as the result ofthe deformations of the tool or of the tool holder. Consequently, duringsubsequent machining of the gearwheels optimal work results are obtainedwithout further measures being required. Therefore the tool according tothe invention and the method according to the invention are particularlysuitable for series machining of workpieces in the form of gearwheels,because on the basis of the determination of workpiece or workpieceholder once determined in work step a), adjusting the position of theadjustable blade, carried out, in each instance, in work step b), holdstrue for all workpieces of a series that have the same form (work stepc)).

According to an embodiment of the invention that is appropriate forpractice, the distance between the blades, measured in the longitudinaldirection of the tool carrier, i.e., axis-parallel to the centrallongitudinal axis of the tool, corresponds to at least four times thelength of the blades, wherein distances between the blades thatcorrespond to at most fifteen times the width of the blades cover themachining tasks that usually occur in practice.

In this regard, the width B of the blades, measured in the longitudinaldirection, typically amounts to at most 20% of the length of the toolcarrier, wherein in practice, the blades have a width of typically atleast 5 mm. Therefore, the tool carrier of a tool according to theinvention typically has a length of at least 25 mm, in particular atleast 30 mm, wherein lengths of up to 200 mm cover the machining tasksthat occur in practice. In this regard, the diameters of the toolcarriers of tools according to the invention typically amount to up to50 mm, so that the ratio Lwt/Dwt formed from the length Lwt and thediameter Dwt typically amounts to 0.5-4.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the invention will be explained in greater detailusing a drawing that shows an exemplary embodiment. The figures show,schematically and not to scale, in each instance:

FIG. 1 is a tool for producing back-tapers on teeth of a gearing of asliding sleeve, in a perspective representation;

FIG. 2 is the tool according to FIG. 1 in a frontal view; and

FIG. 3 is the tool according to FIG. 1 in a top view from above.

DESCRIPTION OF THE INVENTION

The tool 1 for producing back-tapers comprises an elongated tool carrier2 in the manner of a journal, which has a cylindrical basic shape and isoriented coaxial to the central longitudinal axis L of the tool 1. Thecentral longitudinal axis L of the tool 1 coincides with the axis ofrotation about which the tool 1 serves during use.

The tool carrier 2 is carried by a mounting pin 3, which serves forclamping the tool 1 in a tool holder, not shown here, of aconventionally configured machine tool, also not shown here. Thediameter Dz of the mounting pin 3 is greater than the diameter Dwt ofthe tool carrier 2, while the length Lwt of the tool carrier 2, measuredaxis-parallel to the longitudinal axis L, is about 3.5 times as great asthe length Lz of the mounting pin 3, also measured axis-parallel to thelongitudinal axis L. The transition between the tool carrier 2 and themounting pin 3 is formed by a shoulder 4 configured in the manner of acircumferential collar, the diameter of which is greater than thediameter Dz of the mounting pin 3, so that the shoulder 4 projectsradially outward beyond the mounting pin 3 and forms a stop, up to whichthe mounting pin 3 can be pushed into the tool holder, not shown, foruse.

Two blades 5, 6 are attached to the tool carrier 2, which blades producetwo back-tapers simultaneously during use on a tooth flank of the toothto be machined, in each instance, of a sliding sleeve not shown here, byremoving material of the tooth. In the example shown here, theback-tapers are formed with mirror symmetry with reference to the widthof the tooth surface. However, they can also be arranged or configuredin asymmetrical manner.

For this purpose, a recess 7 is provided in an end region of the toolcarrier 2, which region borders on the shoulder 4 and is assigned to themounting pin 3, in which recess a carrier element 8 sits with precisefit. This carrier element 8 has a curved outer surface, which fits intothe outer contour of the cylindrical tool carrier 2. The carrier element8 is fixed in place on the tool carrier 2 by means of screws 9, 10. Onits one edge, which is oriented parallel to the longitudinal axis L, theblade 5 sits in a cut-out 11 of the carrier element 8 and is fixed inplace there by means of the carrier element 8, in terms of its locationand angular position 13 with reference to the longitudinal axis L of thetool carrier 2.

For fastening the second blade 6 in place, a further recess 13 isprovided in an end region adjacent to the free end face 12 of the toolcarrier 2, in which recess a carrier element 14 sits with precise fit,which element is shaped in accordance with the carrier element 8, insuch a manner that its outer surface fits into the outer contour of thetool carrier 2, and it is fixed in place on the tool carrier 2 by meansof a screw. In this regard, the blade 6 is held by an insert piece 15,which sits in a recess 16 of the carrier element 14. The recess 16extends in the circumferential direction U of the tool carrier 2 and issupplemented by a recess 17 that is formed in the tool carrier 2. Inthis way, the angular position ß′ of the blade 6 with reference to thecentral longitudinal axis L and, accompanying this, with reference tothe angular position 13 of the fixed first blade 5 can be adjusted bymeans of displacement of the insert piece 15 in the circumferentialdirection U, within the recesses 16, 17.

In addition, the insert piece 15, with the blade 6 that is carried by itand is adjustable in terms of its position, can be adjusted in theradial direction R with reference to the central longitudinal axis L.Fixation of the insert piece 15 and of the blade 6 in the correspondingangular position ß′ and of the corresponding radial position on the toolcarrier 2 in turn takes place by means of a screw 18.

The blades 5, 6 are oriented in the longitudinal direction LR of thetool carrier 3 and with mirror symmetry relative to one another, in eachinstance. In this regard, the blades 5, 6 have a lesser thickness ontheir narrow sides that face away from one another, than on their narrowsides that face one another, so that the cutting edges 5 a, 6 a of theblades 5, 6 are oriented at a slant with reference to the orientation ofthe central longitudinal axis L.

The distance A between the wider narrow sides of the blades 5, 6, whichare assigned to one another, approximately corresponds to six times thewidth B of the blades 5, 6, measured axis-parallel to the longitudinalaxis L, and their width B in turn corresponds to approximately 10% ofthe length Lwt of the tool carrier 3, in each instance.

In the reference position, the center lines MS of the blades 5, 6 areoriented on a line ML that is oriented axis-parallel to the centrallongitudinal axis L. In this orientation, back-tapers on the tooth flankof the tooth to be machined, in each instance, which optimally have thesame structure, are obtained.

During use, deformation of the tool carrier 2 due to torsion (FIG. 2 )or bending (FIG. 3 ) can occur due to the transverse forces and momentsthat occur during chip-removing machining of the teeth of the gearing tobe machined.

In the event of torsion, the tool carrier 2 twists more toward its frontfree end face 12, counter to the direction of rotation DR, than in itsend region, which is assigned to the mounting pin 3. As a result, theangular position ß′ of the blade 6 assigned to the free end face 12,with reference to the central longitudinal axis L, would deviate fromthe angular position ß=0° of the non-adjustable blade 5, assigned to themounting pin 3, which also relates to the central longitudinal axis L,counter to the direction of rotation DR by an amount of angle Δß, unlesscounter-measures were taken. The position of the blade 6 that resultsfrom this is indicated with broken lines in FIG. 2 .

To balance out this change in the position of the adjustable blade 6that occurs due to the torsion deformation of the tool carrier 2, ascompared with the reference position, the insert piece 15, with theblade 6, is displaced in the circumferential direction U in thedirection of rotation DR by the amount of angle Δß. In the non-used,unstressed state, the position of the blade 6 therefore deviates fromthe reference position. During use, however, the blade 6 is in itsreference position as the result of the torsion deformation of the toolcarrier 2 that then occurs, in which position it is oriented in linewith the fixed blade 5. In the event of small deviations, the change inposition of the blade 6, which results from the torsion deformation andfundamentally follows an arc shape, can be approximated by means of alinear adjustment transverse to the longitudinal axis L of the tool. Ifit turns out that in spite of the adjustment that takes place in thismanner, the change in position of the blade 6 that results from torsioncannot be balanced out, then for equalization, repositioning of theblade 6 that follows the arc shape can be undertaken.

In the event of bending, either the tool carrier 2 itself is bent towardthe free end face 12 or the tool holder, not shown here, is deformed insuch a manner that the longitudinal orientation of the longitudinal axisof the tool carrier 2 deviates from the reference position of thecentral longitudinal axis L. The deformation that occurs as a result isshown with broken lines in FIG. 3 . Accompanying this, the radialposition r′ of the blade 6, with reference to the longitudinal axis L,would deviate from its radial reference position r by a distance of Ar.

To balance out this deviation, the insert piece 15, with the blade 6, isoffset outward by the amount Δr in the radial direction R, withreference to the central longitudinal axis L, so that when the tool 1 isnot in use, the position of the adjustable blade 6 deviates from itsreference position, but in use, i.e., during machining of the teeth ofthe sliding sleeve, the blade 6 is in its reference position due to thechange in its position that occurs as the result of the bendingdeformation that then occurs.

REFERENCE SYMBOLS

-   -   1 tool for producing back-tapers    -   2 tool carrier of the tool 1    -   3 mounting pin of the tool 1    -   4 rotating shoulder of the tool 1    -   5 fixed, non-adjustable blade of the tool 1    -   5 a, 6 a cutting edges of the blades 5, 6    -   6 variably adjustable blade of the tool 1    -   7 recess of the tool carrier 2    -   8 carrier element    -   9, 10 screws for attachment of the carrier element 8    -   11 cut-out of the carrier element 8    -   12 free end face of the tool carrier 2    -   13 recess of the tool carrier 2    -   14 carrier element    -   15 insert piece carrying the blade 6    -   16 recess of the carrier element 14    -   17 recess of the tool carrier 2    -   18 screw for fixation of the insert piece 15    -   ß angular position of the blade 5 with reference to the        longitudinal axis L    -   ß′ angular position of the blade 6 with reference to the        longitudinal axis L    -   Δß amount of angle    -   Δr distance    -   A distance between the blades 5, 6    -   B width of the blades 5, 6    -   DR direction of rotation of the tool 1    -   Dwt diameter of the tool carrier    -   Dz diameter of the mounting pin 3    -   L central longitudinal axis of the tool 1    -   LR longitudinal direction    -   Lwt length of the tool carrier 2    -   Lz length of the mounting pin 3    -   MS center lines of the blades 5, 6    -   ML line oriented axis-parallel to the central longitudinal axis        L    -   U circumferential direction of the tool carrier 2    -   R radial direction R

1. A method for simultaneously producing at least two back-tapers onteeth of a gearing of a workpiece in a form of a gearwheel using a toolthat rotates about a central longitudinal axis, wherein the toolcomprises: a tool carrier configured in an elongated manner, in a mannerof a journal, and oriented coaxial to the central longitudinal axis ofthe tool; and at least two blades, which come into engagement with atooth to be machined, removing chips during use, wherein the at leasttwo blades are held on the tool carrier at a distance from one anotherin a longitudinal direction of the tool carrier, and wherein a width ofeach of the at least two blades extends over a partial length of thetool carrier, wherein a position of at least one of the at least twoblades is adjustable in relation to the other of the at least twoblades, so as to balance out deformations of the tool carrier that occurduring use, and at least the following work steps are completed toproduce the at least two back-tapers, a) determining a bendingdeformation and/or a torsion deformation that the tool carrier or aclamp in which the tool is held experiences during production of the atleast two back-tapers; b) adjusting a position of the adjustable bladeof the tool with reference to the other blade of the tool taking, intoconsideration the deformation determined in work step a), in such amanner that the position and a shape of the at least two back-tapers tobe produced on the teeth of a gearwheel type meet a required value; andc) producing the at least two back-tapers on the teeth of the workpiece.2. The method according to claim 1, wherein the workpiece is a slidingsleeve for a manual transmission.
 3. The method according to claim 1,wherein at least one of the at least two blades is adjustable in aradial direction with reference to the central longitudinal axis.
 4. Themethod according to claim 1, wherein at least one of the at least twoblades is adjustable in a circumferential direction of the tool carrier.5. The method according to claim 1, wherein the distance between the atleast two blades, measured in the longitudinal direction of the toolcarrier, corresponds to at least four times the width of the at leasttwo blades, measured in the longitudinal direction of the tool carrier.6. The method according to claim 1, wherein the width of the at leasttwo blades, measured in the longitudinal direction of the tool carrier,amounts to at most 20% of the length of the tool carrier.